Black Mould in New Zealand
That dark patch could be Stachybotrys, the so-called toxic black mould, or one of a dozen look-alikes. A lab test tells you which.
See your testing optionsWhy Identifying Black Mould Matters
"Black mould" is one of the most common home health worries in New Zealand, and our damp climate lets mould grow year-round, from Auckland to Invercargill. What most people don't realise is that the "toxic black mould" you may have read about is just one of many dark moulds, and you can't tell them apart by eye. Finding out which one you have tells you how serious it is and what to do next.
Scaada NZ offers black mould identification, lab testing and mould assessments anywhere in New Zealand. Courier a sample to our Hamilton lab, or have one of our assessors visit.
Two Ways to Find Out for Certain
Most people start with a lab test by post: it's the cheapest way to get a definite answer. If the problem is bigger, or you need a report for insurance, a tenancy or a sale, an on-site assessment goes further.
Post-in lab test
You take the sample, and we identify it under the microscope.
$250 + GST, kit of three
Three Bio-Tape slides, analysis of all three included · qualified-analyst report in 3 business days
- We post you a kit of three Bio-Tape slides with simple instructions. Or take a lift with your own clear tape and post it to us, from $150 + GST
- Identifies the mould and measures how much is there (ASTM D7658-17)
- Confirms whether it's Stachybotrys or a look-alike
- A report you can show your landlord, insurer or GP
On-site assessment
We come to you for the full picture, including the moisture source.
from $800 + GST
Multi-area sampling · moisture mapping · IICRC S520 report
- Air & surface sampling across the property
- Moisture readings that locate the water source, not just the mould
- Best for health symptoms, bigger areas, or insurance & legal matters
- Carried out nationwide by us or our trusted assessor network
1 · We post your kit
Tell us your region and we'll send a tape-lift kit with step-by-step instructions (you can read them here first).
2 · Take a sample, courier it back
Lift a sample from the affected area and send it to our Hamilton lab overnight.
3 · Get your report
A clear result from our qualified mould analysts in 3 business days: what it is, and what to do next.
Not sure which fits? Call or text 022 315 1171, or see the full sample submission process.
What "Black Mould" Actually Is
When people say "black mould" or "toxic black mould", they almost always mean Stachybotrys chartarum. It only grows where materials stay wet for a long time, and it feeds on cellulose-rich materials such as plasterboard, timber, paper and fabric. So finding it is a strong sign of long-term water damage or an ongoing leak, not just high humidity.
It is a genuine concern because it can produce mycotoxins called trichothecenes. Its spores don't float easily, but tiny fragments carrying mycotoxins can get into the air, so people can be exposed even when the growth is hidden behind a wall or under a floor.
Is It Really Black Mould? Common Look-Alikes
Every mould below can look like a dark patch on a wall. Under the microscope they are easy to tell apart, and they have very different health risks and clean-up needs, which is why guessing by eye isn't enough. All the images are real microscopy from the Scaada NZ laboratory.
Stachybotrys
The true "toxic black mould". It only grows after long-term water damage, and produces trichothecene mycotoxins.
Aspergillus
Tiny spores (2–5 μm) that can be breathed deep into the lungs. A common allergy trigger, and a cause of lung infection (aspergillosis) in people with weakened immune systems.
Penicillium
Common and fast-spreading, and mainly an allergy trigger. Some strains produce mycophenolic acid, which suppresses the immune system.
Cladosporium
One of the most common moulds indoors. Usually lower risk, but you can't tell that by eye.
Ulocladium / Alternaria
A strong asthma trigger, especially in children. Growth indoors points to water damage.
Chaetomium
A water-damage mould that produces mycotoxins and has been linked with asthma.
Same colour, very different problem. Only lab microscopy, to methods such as ASTM D7658-17, can tell you which one is on your wall and what it means for your health.
Black Mould Health Risks, and Who Is Most at Risk
Health effects depend on which mould it is, how much there is, how long you're exposed and how sensitive you are. Most people have mild symptoms or none, but some people are more at risk.
Allergy and breathing symptoms
Sneezing, itchy eyes, skin irritation and a runny or blocked nose, through to asthma flare-ups and a cough that won't go away.
Mycotoxins
Stachybotrys and Chaetomium produce mycotoxins. Their effects at the levels found in homes are still being researched, but they're a good reason to deal with the growth promptly.
Immune sensitisation
Repeated exposure can sensitise the immune system and, in some people, lead to hypersensitivity pneumonitis (inflammation of the lungs).
Most at risk: babies and young children, older people, people with asthma or other lung conditions, people with weakened immune systems, and pregnant people. Read more in mould and your health.
Found something dark and you're not sure?
Send us a sample from anywhere in New Zealand, or book an on-site assessment. Either way you get a clear report from qualified mould analysts telling you exactly what it is and what to do next.
What the Guidance Says (BRANZ & Healthy Homes)
You don't have to take our word for it. New Zealand's building and tenancy guidance all says the same thing: mould is a moisture problem first.
- BRANZ (Building Research Association of NZ) is clear that indoor mould is driven by excess moisture, and that lasting control comes from fixing the source (ventilation, heating and stopping water getting in), not from wiping the surface.
- Healthy Homes Standards 2019 require rental properties to meet minimum standards for heating, insulation, ventilation, moisture ingress and drainage, and draught-stopping: exactly the conditions that stop mould taking hold.
- NZS 4303:1990 recommends keeping indoor humidity below 60%. Readings that stay above that let mould grow even on surfaces that look dry.
A lab report gives you independent, written evidence that carries weight with a landlord, an insurer, a remediator or your GP.
Found Suspected Black Mould? Do This
Before you reach for the bleach, the order you do things in matters. Getting it wrong can spread the problem.
- Don't disturb it. Scrubbing or dry-brushing releases spores (and, with Stachybotrys, mycotoxins) into the air. Leave it until it's assessed.
- Don't just bleach it. Bleach only treats the surface. The mould's root-like threads (hyphae) grow into porous materials and regrow, and you still won't know which mould it was.
- Get it tested. Take a surface sample with a tape-lift kit (we'll send one, and the step-by-step instructions are here), or book a professional on-site assessment with moisture readings.
- Fix the moisture source. Whether it's a leak, condensation, rising damp or poor ventilation, mould comes back after any clean-up unless the water is dealt with.
- Use qualified remediators for bigger jobs. For areas over 1 m², remediation to IICRC S520 standards is recommended, with a Post-Remediation Verification to confirm it worked.
Read why bleach (and vinegar) don't kill mould, with lab samples taken after DIY clean-ups.
How We Confirm It
Our qualified mould analysts and occupational hygienists identify exactly what's present and how serious it is, then report it against the IICRC S520 condition ratings.
Surface sampling
A tape lift picks up a 4 cm² sample with the spores and hyphae intact. Under the microscope (ASTM D7658-17) we identify the mould and see whether it is actively growing there or has settled from elsewhere.
Air sampling
Spore-trap cassettes measure what's in the air, compared with an outdoor sample taken the same day to show whether indoor levels are really high.
Moisture & environment
Moisture, temperature and humidity readings, taken without damaging anything, track down the water feeding the mould.
Condition 1 · Normal
Typical of a healthy indoor environment. No remediation required.
Condition 2 · Settled spores
Elevated spores settled from elsewhere. Cleaning advised; find the source.
Condition 3 · Active growth
Confirmed colonisation. Professional remediation recommended.
Black Mould FAQ
Is black mould dangerous in New Zealand homes?
It can be. Stachybotrys chartarum, the mould usually meant by "black mould", produces mycotoxins called trichothecenes, and damp, mouldy homes are linked with allergies, asthma and other breathing problems, especially for children, older people and anyone with a lung condition or a weakened immune system. But most dark mould isn't Stachybotrys, and only a lab test can tell you which mould you have and how much of a concern it is.
How do I test for black mould in my house?
You can take a surface sample yourself with a tape lift kit (contact us and we'll send one with instructions), or book an on-site assessment for a full investigation. We examine samples under the microscope to ASTM D7658-17 to identify which moulds are present. Air sampling can also show whether spore levels indoors are higher than outside.
What should I do about black mould in my rental property?
Under the Healthy Homes Standards, landlords must deal with moisture and ventilation. If you find suspected black mould, don't disturb it, tell your landlord in writing, and consider getting it tested. A lab report records which moulds are present and how much, giving you independent evidence for talks with your landlord or property manager.
What does black mould look like?
Stachybotrys usually appears as dark greenish-black patches that look slimy or wet while it is growing. But Aspergillus, Penicillium, Cladosporium and Ulocladium can all look dark or black too. You can't identify it reliably by eye; only lab microscopy can confirm which mould it is and what it means for your health.
Can I remove black mould myself?
For small areas of surface mould (under 1 m²), careful cleaning with suitable products may be enough, but it's still worth testing first so you know what you're dealing with. For areas bigger than 1 m², or if mould keeps coming back, use a professional remediator. Stachybotrys in particular shouldn't be disturbed without proper containment, because disturbing it releases fragments carrying mycotoxins into the air.
Order a Test Kit or Ask Us
Tell us about your situation. To order a test kit ($250 + GST), choose "Request a test kit" below and we'll post one out.
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